1. Field of the Invention
This invention relates to improvements in insulating devices and more particularly, but not by way of limitation, to an automatic insulating shutter for attic fans and other horizontally mounted type fans.
2. Description of the Prior Art
Attic fans and other exhaust type fans normally include an exhaust opening through which air is exhausted from an enclosed area. All attic fans are manufactured with a mounting frame and because of their size and considerable weight are normally secured to and rest upon the studs of the ceiling. The closest distance between the horizontal plane of the ceiling where the shutter is attached and the blades of the fan normally does not exceed 101/2 inches. The size of the exhaust opening in the ceiling is normally calculated to accommodate the size of the fan's housing frame. Ideally, of course, the fan is designed to operate without any restrictions between the fan blades and the air it evactuates. Therefore, any type of shutter device restricts the efficiency of the fan and encumbers the fan's drive motor. Most, if not, all shutters are manufactured out of very light metal and in a rectangular shape with the lift up panels running across the short side of the rectangle. Since the lift up panels are dependent, one upon the other, by lapping over each other to complete the closure function when the fan is deactivated, they are pivotally attached to one another usually by a bar or bars running the longside of the rectangle so that they may open and close in unison. The lift up panels are enclosed and confined to operate within the mounting frame of the shutter. When the fan is activated the panels lift up in unison into the space above the horizontal plane of the mounting frame of the shutter and the lifting of the panels by the fan is usually assisted by a spring means attached from the mounting frame to the lift up bar. The lift up panels are made to stop substantially short of a full open position to insure that gravity will pull the panels back into a closed position when the fan is deactivated. There are many closure devices for use in combination with the exhaust ports of these fans and which automatically open and close upon the activation of deactivation of the respective fan. Whereas these closure devices have been satisfactory in the past, the current energy problem has increased the importance of reducing loss of warm or cold air through these closure devices. As a result, certain insulating closure assemblies have been developed to reduce the heat dissipation or heat loss through the exhaust openings either from the interior of the enclosed area, or from the exterior thereof. For example, Chapman U.S. Pat. No. 3,964,377, issued June 22, 1976, discloses an insulated closure for attic fans and seals therefor. The Chapman closure includes insulating panels pivotally secured within the attic fan opening and responsive to the draft created by the actuation of the fan for moving to an upwardly extending angular position for permitting the flow of air through the opening. When the fan is deactivated, the panel or panels return to a closed position in the opening. In addition, peripheral sealing members are interposed between each of the panels themselves and the panels and the frame of the opening for precluding the escape of air therebetween in the closed position of the panels. The lift up panels of the Chapman device are just like those on any standard shutter except the addition of insulation material and seal strips, in that they are dependent upon one another by lapping each on the other to complete the closure when the fan is deactivated; they are attached to one another so that they act in unison in opening or closing; they are pivotally secured within and are designed to operate within the confines of the mounting frame of the shutter assembly; when the fan is activated they rise up inside the space above the horizontal plane of the mounting frame; and the panels are stopped short of full opening because of the closure function is solely dependent upon the pull of gravity. In Chapman, therefore, having a given space within the confines of the mounting frame to operate, it follows that as the thickness of the panels is increased in order to accomplish more insulation function than the open air space between each of the panels is correspondently decreased, thereby further restricting the air flow through the fan. In order to afford any reaslistic insulating function in the Chapman device, the panels would have to be made so thick that the corresponding restriction of the air flow between the panels would drastically reduce the efficiency of the fan, and therefore, largely destroy the primary purpose of the fan, that is, to evacuate a desired volume of air. Also these insulating panels do not fully open, and as a result, there is some added restriction in the flow of air through the opening, and in addition, normal draft conditions or pressure differentials across the panels in the closed position thereof, may cause the panel to flutter, and as a result, there is undesirable loss of air therethrough.
Additional insulated closure members are shown in the Mayr U.S. Pat. No. 2,571,374, issued Oct. 16, 1951; the Pfautsch U.S. Pat. No. 2,579,395, issued Dec. 18, 1951; and the Koch U.S. Pat. No. 2,580,797, issued Jan. 1, 1952. These patents all disclose a hinged flapper member adapted to engage the outer end of a draft opening of a ventilating duct, the hinged flapper being of an insulating type. However, these flapper members are mounted in a vertical position; do not provide a substantial full opening; are made to operate entirely outside the confines of duct; and do not employ the use of an intermediate frame to allow the flapper to extend into and outside of the duct when the fan is activated. In the case of the Mayr and Pfautsch devices, and the flapper of the Koch device is provided with manual means for overcoming the biasing spring in order to open the flapper. Still another patent, namely the Emmert U.S. Pat. No. 2,367,265, shows a ventilation port installed as an auxiliary feature to a window, the ventilation port having louvers provided therein which may have insulating inserts provided. These louvers may be opened and closed manually, or the like, when it is desired to ventilate an enclosed area, or open the area to the atmosphere.